Trestle bridge



J. A. DOR'ST TRESTLE BRIDGE Sept. 3, 1946.

Filed Dec. 17, 1945, 5 Sheets-Sheet l W AEH mil NNI

mm m mm James A; Dorsf Sept. 3, 1946. J. A. DORST TRES'TLE BRIDGE Filed Dec. 1'7,- 1943 3 Sheets-Sheet 2 Sept, 3, 1946. v J. A; DORST 5 TRES'ILE BRIDGE Filed Dec. 17, 194: 35heets-Shaat s Patented Sept. 3, 1946 'TRESTLE BRIDGE James A.f'l)orst, United States Army, Geiger Field, Wash.

.ikpplicationiDecember 1'7, 1943, Serial No.:514;613

(OLE- 1) (Granted under the act of March '3, 1883, as

1 The invention described 'hereinmay be manufactured and used by or forthe Government for governmental ,purposes, without payment to me of any royalty thereon.

"Thisinveritionrelates to a bridgeandthe primary object thereof is 'to provide a device of this character .h'av'ing prefabricated parts which may be readily Jtransported to a body of 'water and speedily erected for facilitating the passing of vehicles and "the "like 'there'over "and quickly llmoc'ked down foritranspo'rt'ation and assemblyat other places. I

Another object or the invention is to provide a bridge structure of fewiparts, whichmay *be easily replaced or speedily repaired upon bein damaged, quickly modified to "carry?heavy loads and the. parts may be assembled'together in'such a manner as to form .aunitary'bridgestructure without substantially anyn'ois'e.

The invention is directed.nfore'p'articularlyto a trestle bridge for use by army engineers in spanning bodies of water whereby vehicles "may pass over the same and "briefly comprises .long'itudinally extending spaced treadways "and guide rails supported on bents including transversely extending transoms vertically adjustably mounted thereon, with each of the treadways being made of a plurality of sections of spaced stringers overlapping at their ends, and having filler blocks therebetween, said stringers and guide rails being detachably secured together by clamps.

With the above and other objects and advantages in view the invention consists of certain features of construction and operation of parts which will hereinafter be shown in the accomextending uprights or trestle columns I and a transom or horizontally extending beam 2 adjustably mounted thereon. The uprights or trestle columns I are each formed of a pair of parallel bars I held in spaced relation by blocks 3 and having mud shoes or footings I on their lower amended April 130, 19-28; K370-'O.G. 757) ends, which fmu'd shoes or footings '4 areadapte'd 'to'engage the bottom 5of a river :bed or the like.

The ends of the transomsZ extend between the 'pairsof "spaced trestle barsI" and are supported on "cross pieces 6 mountedbetween,frictionblo'cks 1 "of clamp members indicated generally by The clamp members *8 also include frictiontblocks 9 pivotally connected through the links "I0 and the bolt I I by staples Ila/to "thefricti'onblocks I.

The bents A are 'p'rovide'd'with knee braces I-2 having side members I3 mounted on their upper ends, .whichside members I 3 engage opposite sides of the transoms 2 andaresecuredtheretoby'bolts I4. The upper ends :of the'knee braces I2 abut against the "lower :edges I5 of the transoms 2 and "the lowerends of the'knee braces are-secured by bolts 16a or .other suitable means .to the lower ends of the friction blocks .1. Strap members -II secured to the friction blocks "I by means of bolts I6 are adapted to engage detachablythe trestle columns I. The lower ends of the braces I2 extend between the pairs of spaced bars rI' forming "the trestle columns]. The 'transoms 2 support dual suitably. spaced treadwaysindicated generally by B, with each itreadway consisting of a plurality of sections I8 of longitudinally extending stringers I9 seated at their bottom edges on the transoms 2. The stringers I9 of each treadway are in suitable spaced relation and are of sufficient length to more than span the bents A. The ends of one section I8 of stringers I9 extend between the ends of another section of stringers or in other words the ends of one section of stringers I9 overlap the ends of an adjacent section of stringers. Filler or spacer blocks 20 are provided between the stringers I9 at midspan and guide rails 2| are provided, said guide rails 2I being of a greater height than the stringers I9 and are positioned adjacent the innermost stringer of each treadway.

The stringers I9 and guide rails 2] are detachably secured together by means of suitably spaced clamps 22, each consisting of a pair of bolts 23 having end plates 24 mounted thereon, said clamps 22 being arranged in a vertical plane with the bolts 23 extending horizontally across the stringers I 9 and through the guide rails 2I.

The upper ends of the trestle columns I of the bents A are provided with grooves 25 which are engaged by safety ropes or cables 26 secured to the friction blocks 9 and safety ropes or cables 26' are attached to the ends of the transoms 2 and to the upper ends of the trestle columns I. The safety ropes or cables may be attached only to the transoms 2 and the upper ends of the trestie columns I if desired. Ropes or cables 21 also connect the trestle columns I on the bents A together in a manner as to provide cross bracing for the bridge structure.

The bridge structure above-described can be transported by trucks of normal size to a river or other body of water to be crossed and upon the trucks reaching the selected place, the bents A are positioned therein with the mud shoes or fioorings 4 engaging the bottom 5 of the river bed. The clamp members 8 are moved vertically upward on the trestle columns I to the desired height by means of safety ropes 26 while the strap members ll engage the trestle columns I and serve as guides. The transoms 2 and the roadway B are then placed in position with the transoms 2 supporting the roadway B and resting on the crosspieces 6 and the knee braces l2. The Weight of the transoms and the roadway acting on the crosspieces 6 tend to force the blocks 1 downwardly and by means of the links l0 cause the blocks 1 and 9 to grip the trestle columns I tightly. After the transoms 2 have been placed in position and the roadway B mounted thereon, the stringers I9 and the guide rails 2| are detachably secured together by the clamps 22, after which the cross bracing ropes or cables 21 are secured to the trestle colurrms I as illustrated in Fig. 1.

By placing thefiller blocks 20 between the stringers [9 at substantially mid-span the utmost eiliciency results. There is no flooring used on the stringers l9, as the upper edges thereof serve that purpose and with this arrangement of the stringers to form the treadways a certain degree of continuous-beam action is provided, thereby short stretches of deep water the bridge may be erected from one end only at a predetermined number of feet per hour and the longer the crossing the faster the speed of assembly, as the bridge may be then erected from any suitable number of ends. The bridge may also be easily and simply modified to carry heavy loads by halving the span between bents having a certain number of extra trestle columns added thereto. If desired, the stringers l9 may be laid on transoms mounted on pontoons in providing a span across a body of water.

It will thus be seen that there is provided a novel and useful form of bridge structure which is well adapted for the purpose intended. Even though there has herein been shown certain features of construction and operation of parts, it is nevertheless to be understood that various changes may be made therein, if the changes do not depart from the spirit or scope of the claims.

Having thus described my invention, what I claim as new and wish to secure by Letters Patent is:

1. In a bridge structure of the class wherein a roadway is supported by a vertically adjustable transom arranged transversely between a pair of trestle columns positioned at opposite sides of said roadway, the combination with a trestle column and a transom, of a vertically adjustable transom support comprising a pair of friction blocks slidably disposed on opposite sides of said trestle column, one of said friction blocks being adapted to support said transom, suspension means for supporting the other friction block at a predetermined point on said trestle column and link means pivotally connecting said friction blocks, said link means being operably responsive to the weight of said transom on said transom supporting friction block for clamping each of said friction blocks on said trestle column.

2. A bridge structure as set forth in claim 1 characterized in that one of said friction blocks is provided with a knee brace adapted to engage said transom.

JAMES A. DORST. 

